JP3422336B2 - Method for producing esters - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various uses such as fragrances, jet engine oils, low-temperature greases, heat-resistant engine oils, refrigerator oils, rubbers, inks, and paint additives. The present invention relates to a method for producing esters used, and more particularly, to a method for producing esters from olefin, carbon monoxide and alcohol. [0002] Conventional esters are disclosed, for example, in JP-A-5-5
As described in No. 098, it is produced by heating a fatty acid and an alcohol in the presence of a catalyst to perform a dehydration reaction. As a catalyst used for this dehydration reaction, an acid catalyst such as sulfuric acid and paratoluenesulfonic acid and an organic titanate compound such as tetrapropyl titanate are known. This dehydration reaction is an equilibrium reaction, in which excess alcohol is used and the reaction is promoted by removing generated water from the reaction system. However, the reaction speed is generally slow, and a long time is required to complete the reaction. For example, when producing an ester from a branched fatty acid such as a neo-acid type, it is necessary to react at a high temperature of 200 ° C. or more for 10 hours or more, and a high-capacity, large-capacity reactor is used. large. In order to avoid such a reaction at a high temperature for a long time, Japanese Patent Application Laid-Open Nos.
No. 1291 proposes a method for producing an ester via an acid chloride. However, such a method of esterification via an acid chloride requires the production of an acid chloride from a carboxylic acid first,
For this purpose, acid chlorides of inorganic acids such as phosphorus trichloride, phosphorus pentachloride and thionyl chloride are used. Acid chlorides of these inorganic acids are difficult to handle and require complicated steps. [0004] The present inventors have previously found that esters can be produced efficiently by reacting an olefin, carbon monoxide and an alcohol in the presence of hydrogen fluoride. (Japanese Patent Application No. 5-143679)
. In this method, esters can be obtained in a high yield in a short reaction at a low temperature, but various by-products are produced by polymerization of unsaturated hydrocarbons (olefins) and reaction with carbon monoxide, alcohols and the like. In addition, the yield of the esterification reaction is limited, and many distillation columns are required to separate the desired esters. An object of the present invention is to solve such a problem in producing an ester by reacting an olefin, carbon monoxide and an alcohol in the presence of hydrogen fluoride, and to efficiently produce a high-purity ester. It is an object of the present invention to provide a method for producing an industrially advantageous method. [0006] The inventors of the present invention have conducted intensive studies on a method for producing an ester having the above-mentioned problems, and as a result, have found that the above-mentioned ester production process can be carried out in the presence of hydrogen fluoride in the presence of an olefin. And a process for synthesizing an acyl fluoride by the reaction of carbon monoxide and an esterification process for reacting the obtained acyl fluoride with an alcohol, and the reaction solution from the acyl fluoride synthesis process is distilled under reflux of a saturated hydrocarbon. As a result, it has been found that the operation time of the esterification reaction is shortened, the yield is improved, and the separation and purification of the esters is extremely easy. That is, the present invention relates to a process for producing an ester by reacting an olefin, carbon monoxide and an alcohol in the presence of hydrogen fluoride.
An olefin, an acyl fluoride synthesis step of reacting carbon monoxide, (ii) an acyl fluoride distillation step of distilling the obtained reaction solution together with an inert saturated hydrocarbon having a higher boiling point than the acyl fluoride, and (iii) A method for producing esters, comprising an esterification step of reacting a mixed solution of hydrogen fluoride and acyl fluoride separated in the distillation step with an alcohol. The olefin used as a raw material in the present invention includes propylene, butylene, isobutylene, pentene, hexene, octene and the like. Alcohols used as other raw materials include monohydric alcohols such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol and octanol, neopentyl glycol, trimethylolethane, trimethylolpropane, and pentaerythritol. And polyhydric alcohols such as ethylene glycol, propylene glycol, glycerol, and sorbidol. The amount of hydrogen fluoride used in the acyl fluoride synthesis step of the present invention is 5 to 30 mol, preferably 7 to 15 mol, per 1 mol of the olefin. When the molar ratio of hydrogen fluoride to olefin is lower than 5, the amount of side reaction increases, and the yield of acyl fluoride and ester decreases. If the molar ratio is higher than 30, the yield is not changed and the reactor becomes large, so that it is not economically advantageous. In the present invention, a catalyst obtained by adding boron trifluoride to hydrogen fluoride can also be used. [0010] The reaction temperature of the olefin and carbon monoxide varies depending on the olefin used, but generally ranges from -30 to 70.
° C, preferably -20 to 50 ° C. If the reaction temperature is too high, by-products increase and the yield decreases. If the reaction temperature is too low, the reaction rate will be low, which is economically disadvantageous. The pressure at which the olefin reacts with carbon monoxide in hydrogen fluoride is 100 kg / cm ² G or less, preferably 10 to 80 kg / cm ² G. When the reaction pressure is low, the yield of acyl fluoride is low. But the pressure is 100 kg / cm
Even if it is higher than ² G, the yield hardly changes and the equipment cost becomes high, so that it is not industrially advantageous. The amount of carbon monoxide used in the acyl fluoride synthesis step is determined by the reaction pressure. Note that the above reaction pressure is the case where high-purity carbon monoxide is used. If the carbon monoxide gas used contains a considerable amount of inert gas, the partial pressure of carbon monoxide is the reaction pressure. Is equivalent to The reaction solution obtained from the acyl fluoride synthesis step becomes a solution of hydrogen fluoride, so that a reaction solvent is not particularly required in this step. However, the solvent (saturated hydrocarbon) used in the next distillation step can also be used in this step. As a method of using a solvent, for example, there is a method of dissolving an olefin in a solvent and supplying the solution to a reactor. The saturated hydrocarbon used as a solvent for the distillation of acyl fluoride from the acyl fluoride synthesis step in the present invention is a saturated hydrocarbon having a boiling point higher than that of acyl fluoride and being inert to acyl fluoride. , Hexane, heptane, octane, nonane, decane and the like. In this distillation step, the reaction product liquid from the acyl fluoride synthesis step is distilled under reflux of the saturated hydrocarbon, and the saturated hydrocarbon is supplied from below the acyl fluoride reaction liquid supply port.
Hydrogen fluoride and high-purity acyl fluoride are separated from the top of the distillation column and used in the next esterification step. From the bottom of the distillation column, by-products in the acyl fluoride synthesis step [polymerization of unsaturated hydrocarbon (olefin)] , Etc.) and a saturated hydrocarbon. In this bottom liquid, saturated hydrocarbons are easily separated by distillation and are recycled. The amount of the saturated hydrocarbon used in the acyl fluoride distillation step is 0.5 to 2.0 mol, preferably 1.0 to 1.5 mol per mol of the olefin used in the acyl fluoride synthesis step. Is a mole. If the molar ratio of the saturated hydrocarbon to the olefin is lower than 0.5, it is not possible to obtain a higher purity acyl fluoride than the top of the column. When the molar ratio is larger than 2.0, the amount of energy required for heating increases and the amount of recovery increases, which is not economical.
The distillation temperature varies depending on the olefin and the saturated hydrocarbon used, but is generally 100 to 250C, preferably 120 to 200C at the temperature at the bottom of the column. It is advantageous in terms of process to carry out the distillation under normal pressure or under pressure.
Desirably, the pressure is 5 to 1.0 kg / cm ² G. The amount of the alcohol used in the esterification step is not more than 2 molar equivalents per mole of the olefin (based on the number of moles of the OH group of the alcohol), and is preferably 0.7 to 0.7.
1.5 mol. If the amount of alcohol used is too large, the amount of unreacted alcohol recovered will increase. When the amount of the alcohol used is too small, the yield of the esters decreases. The reaction temperature of this esterification step is -10
To 70 ° C, preferably 0 to 50 ° C. The esterification reaction is carried out under pressure or normal pressure, preferably from 0.5 to 1.
It is 0 kg / cm ² G. The esterification reaction liquid obtained by the method of the present invention is easily separated from hydrogen fluoride by distilling the acyl fluoride reaction liquid in the same manner as in distilling a saturated hydrocarbon under reflux. Then, this hydrogen fluoride can be recycled and used.However, depending on the type of the obtained ester, it is also possible to obtain the esters by charging the reaction product liquid into water and separating the oil layer from the aqueous layer with a specific gravity difference. it can. In the acyl fluoride synthesis step, when an olefin is reacted with carbon monoxide in the presence of HF, an isomerization reaction occurs depending on the type of the olefin, so that the esters obtained in the esterification step are a mixture of isomers. The composition varies depending on the reaction temperature and pressure in the acyl fluoride synthesis step, and suitable reaction conditions are selected. Next, the present invention will be described with reference to the drawings. FIG.
FIG. 1 shows an example of a flow chart of a method for producing an ester according to the present invention. In FIG. 1, first, in the acyl fluoride synthesis process,
Hydrogen fluoride is supplied to the acyl fluoride synthesis reactor 4 from 1, carbon monoxide is charged to a predetermined pressure from the flow path 3, and then olefin is supplied from the flow path 2 to synthesize acyl fluoride. In the subsequent acyl fluoride distillation step, the acyl fluoride reaction liquid flows through the flow path 5 and the saturated hydrocarbon flows through the flow path 6
This is introduced into the acyl fluoride distillation column 7. A packed tower or a tray column is used for the distillation tower 7.In the packed tower, in order to increase the distillation efficiency, the packed tower 8 is divided into an upper packed section 9, a middle packed section 9 and a lower packed section 10, and the acyl fluoride reaction solution is placed in the upper section. Between the filling section 8 and the middle filling section 9, saturated hydrocarbon is supplied between the middle filling section 9 and the lower filling section 10. In the distillation column, HF, acyl fluoride and saturated hydrocarbon vapors are obtained from the top of the distillation column by heating in the reboiler 11, and the vapors are totally compressed in the condenser 13 and enter the separator 14. In the separator 14, HF and acyl fluoride form a complex, and are separated into two layers by a difference in specific gravity from saturated hydrocarbons.
It is extracted and refluxed to the distillation column. H from channel 16
F and acyl fluoride are withdrawn and transferred to the esterification reactor 18. In the esterification step, HF and acyl fluoride are supplied from a channel 16 and alcohol is supplied from a channel 17 to an esterification reactor 18 to carry out an esterification reaction. After the reaction, the esterification reaction solution is introduced into the catalyst recovery distillation column 20 through the flow path 19, HF is recovered from the top 21 and esters are obtained from the bottom 22. Or alternatively, drain into ice water from channel 23,
Esters can also be separated from the oil layer. Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples. Example 1 Two stainless steel autoclaves each having a stirrer, three inlet nozzles at the top and one outlet nozzle at the bottom, and having a capacity of 1 liter and capable of controlling the internal temperature by a jacket,
Esters were produced using a stainless steel distillation column having a tower diameter of 30 mmφ and a length of 1000 mm and filled with a 1/2 inch Teflon Raschig ring. First, after replacing the acyl fluoride synthesis reactor with carbon monoxide, 210 g (10.5 mol) of hydrogen fluoride was introduced. The mixture was cooled to a temperature of −15 ° C. and pressurized with carbon monoxide to 20 kg / cm ² G. While maintaining the same reaction temperature and supplying carbon monoxide so as to maintain the same pressure, 91 g (0.81 mol) of 1-octene is supplied from the gas phase of the autoclave over about 30 minutes, and after the supply is completed. Stirring was continued for about 20 minutes until no absorption of carbon monoxide was observed. The amount of carbon monoxide absorbed by the reaction was 17.6 g (0.63 mol) from the weight difference of the carbon monoxide measuring tank. Next, the obtained acyl fluoride reaction solution and n-decane are supplied to a distillation column, and distillation is performed under reflux of n-decane.
Hydrogen fluoride and acyl fluoride were recovered from the top and transferred to the esterification reactor. By-products and n-decane were extracted from the bottom of the column. In the esterification reactor, 22 g (0.69 mol) of methanol was fed to the pump over a period of about 15 minutes at normal pressure and 0 ° C., and reacted for 2 hours. After the completion of the reaction, the reaction product liquid was drained into ice water to separate an oil layer. When the oil layer was washed with alkali and analyzed by gas chromatography without performing distillation purification, 2-methyl 2-propylpentanoic acid methyl ester 9%, 2,2-dimethylheptanoic acid methyl ester 14%, Methyl 2-ethylhexanoic acid methyl ester 19%, 2-propylhexanoic acid methyl ester 24%, 2-methylhexanoic acid methyl ester
108 g of a mixture of six methyl ester isomers, 26% of methyl ethyl heptanoate and 8% of methyl 2-methyloctanoate were obtained. The ester yield based on the supplied 1-octene was 77.4 mol%. COMPARATIVE EXAMPLE 1 In Example 1, 22 g (0.69 mol) of methanol was supplied to the reactor over about 15 minutes by a pump at a normal pressure and 0 ° C. without distilling the acyl fluoride reaction solution, and the reaction was carried out for 2 hours. Reacted. After the completion of the reaction, the reaction product was drained into ice water, and the oil layer was separated and washed with alkali. When the oil layer was analyzed by gas chromatography, peaks of by-products were observed in addition to the methyl ester. Therefore, only the methyl ester component was separated and obtained by distillation. When analyzed again by gas chromatography, 102 g of a mixture of six methyl ester isomers having the same composition as in Example 1 was obtained. The ester yield based on the supplied 1-octene was 73.0 mol%. Example 2 An esterification reaction was carried out in Example 1 using ethanol instead of methanol, and an ester was obtained in the same manner. As a result, 2-methyl 2-propylpentanoic acid ethyl ester 9%, 2,2-dimethylheptanoic acid ethyl ester 14%, 2-methyl 2-ethylhexanoic acid ethyl ester 1%
9%, 2-propylhexanoic acid ethyl ester 24%, 2-ethylheptanoic acid ethyl ester 26%, mixture of 6 kinds of ethyl ester isomers of 2-methyloctanoic acid ethyl ester 1
17 g were obtained. The ester yield based on the supplied 1-octene was 77.4 mol%. Example 3 In Example 1, an acyl fluoride synthesis reaction was carried out at -15 ° C. using 1-butene instead of 1-octene, and the obtained reaction solution and heptane were supplied to a distillation column to give heptane. Distillation was performed under reflux to recover hydrogen fluoride and acyl fluoride from the top of the column. The recovered solution was subjected to an esterification reaction with methanol for 2 hours, then dropped into ice water, and the oil layer was washed with an alkali. This was analyzed by gas chromatography to find that methyl 2-methylbutanoate was 99% or more and the yield was 69.4 g. The ester yield based on 1-butene fed was 73.8 mol%. Example 4 An ester was synthesized in the same manner as in Example 3 except that the reaction temperature for the synthesis of acyl fluoride was changed to 15 ° C.
The resulting oily layer was analyzed by gas chromatography and was found to be an isomer mixture of 2-methylbutanoic acid methyl ester 95% and 2,2-dimethylpropanoic acid methyl ester 5%, with a yield of 65.0 g. The ester yield based on the supplied 1-butene was 69.1 mol%. Example 5 In Example 1, the reaction between 1-octene and carbon monoxide was carried out as follows.
An ester was synthesized in the same manner except that the pressure was changed to 50 kg / cm ² G. As a result of analyzing the obtained oil layer by gas chromatography, 2-methyl 2-propylpentanoic acid methyl ester 6%, 2,2-dimethylheptanoic acid methyl ester 1
1%, 2-methyl 2-ethylhexanoic acid methyl ester 17
%, 2-propylhexanoic acid methyl ester 25%, 2-ethylheptanoic acid methyl ester 28%, and 2-methyloctanoic acid methyl ester 13% were obtained as an isomer mixture in an amount of 115 g.
The ester yield based on the supplied 1-octene was 82.5 mol
% Met. According to the method of the present invention, in the presence of hydrogen fluoride,
The following effects can be obtained by distilling an acyl fluoride reaction solution synthesized from an olefin and carbon monoxide under reflux of a saturated hydrocarbon and then reacting it with an alcohol. The esterification reaction is carried out at a low temperature and in a short time, the by-products are extremely reduced, and the yield of esters is improved. Since there are few by-products of the esterification reaction, purification is easy and high-purity esters can be obtained. Energy consumption required for heating when recovering hydrogen fluoride of the catalyst by distillation is reduced. Therefore, esters can be produced very advantageously industrially by the method of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an example of a flow chart of a method for producing an ester according to the present invention. [Description of Signs] 4 Acyl fluoride synthesis reactor 7 Acyl fluoride distillation column 18 Esterification reactor 20 Catalyst recovery distillation column

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C07C53 / 42 C07C53 / 42 (56) References JP-A-58-10538 (JP, A) JP-A-58-4036 (JP, A) JP-A-53-40708 (JP, A) JP-A-63-115843 (JP, A) JP-A-60-224653 (JP, A) 58-188836 (JP, A) JP-A-63-115842 (JP, A) JP-A-64-50840 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 67/14 C07C 69/24 C07C 51/58 C07C 51/64 C07C 53/42

Claims (1)

(57) [Claim 1] In a step of producing an ester by reacting an olefin, carbon monoxide and an alcohol in the presence of hydrogen fluoride, (i) in the presence of hydrogen fluoride, An olefin, an acyl fluoride synthesis step of reacting carbon monoxide, (ii) an acyl fluoride distillation step of distilling the obtained reaction solution together with an inert saturated hydrocarbon having a higher boiling point than the acyl fluoride, and (iii) A method for producing esters, comprising an esterification step of reacting a mixed solution of hydrogen fluoride and acyl fluoride separated in the distillation step with an alcohol.